The instant invention relates to an apparatus for inserting documents into envelopes, and more particularly to a mechanism for opening the throats of the envelopes preparatory to documents being inserted into the envelopes.
Apparatus for inserting documents into envelopes is well known. In order to enable documents to be inserted into an envelope, the flap of the envelope must be secured away from the throat of the envelope and the throat needs to be opened (i.e., the front and back panels need to be separated) a requisite amount. There are various techniques which are employed in inserting machines for opening the throat of an envelope, one of which involves the use of vacuum cups to grip the back panel of the envelope and lift it away from the front panel which, together with the flap, is restrained in an inserting position by mechanical devices. Vacuum cups are connected to tubes which are mounted on a support bar which is rotated towards the back panel of the envelope waiting therebelow. Once the vacuum cups reach the envelope, a vacuum is applied and the cups grip the back panel of the envelope. The support bar is then rotated away from the front panel of the envelope, which causes the back panel to be separated from the front panel, thereby opening the throat of the envelope.
In prior art vacuum cup envelope opening devices, the vacuum cups are rotated a predetermined distance away from the front panel of the envelope, regardless of the thickness of the collation to be inserted into the envelope. The fixed amount of rotation results in the vacuum cups, in many instances, moving a greater distance than is necessary, i.e., unnecessary motion, and excessive distortion of the envelope. This is a significant disadvantage of prior art envelope opening devices of this type for the reason that excessive distortion of envelopes resulting from opening the throats too wide is a principal cause of jamming while the collations are being inserted. The less an envelope throat is opened, the less the front and back panels, especially the back panel which is lifted, are distorted, and correspondingly, the less likelihood there is for the collations to jam while being inserted into the envelope.
Thus, there is a need for a vacuum cup envelope opening device that overcomes the foregoing problems by providing a method and apparatus for moving the vacuum cups only the requisite distance for the thickness of the collation to be inserted into an envelope, thereby eliminating excess motion of the vacuum cups and distorting the envelope no more than is absolutely necessary.